An EPUB book file is a collection of files, which hold the resources for an EPUB. EPUBs, just like HTML, can use a number of different languages, fonts, images and other things. A EPUB does not contain executable code. Therefore EPUBs can be opened in any supported EPUB reader, without the need for additional software or plugins. EPUBs are stored in compressed XML files (.epub). In the version 1.0 format, EPub also includes tools for editing the book itself, as well as a number of RDF tools for publishing to the web.
Different EPUB readers may have different ways of presenting the information, but they all are based on a common EPUB document structure, and generally follow W3C guidelines. However, while this format is common to all EPUB readers, it is not universally accepted by all e-book readers. EPUB files can contain a variety of objects, such as text, images, and video, as well as links to external web references. EPUB documents are always contained in a.epub file extension.
The DRM used inside of EPUBs allows only the licensed user to open the particular file. Once the file is opened by the licensed user, the EPUB software keeps and validates the license and encryption keys to prevent any unauthorized copies.
Please note that the 'Calibre EPUB Books' library in calibre can't open these EPUB files. just a few file/book organizations can open these. Contact the E-book/PDF manufacturers if you have any questions on these file types. 7211a4ac4a